15.1.5 Isearch Yanking

Within incremental search, C-y (isearch-yank-kill)
appends the current kill to the search string. M-y
(isearch-yank-pop), if called after C-y, replaces that
appended text with an earlier kill, similar to the usual M-y
(yank-pop) command (see Yanking). Mouse-2 appends
the current X selection (see Primary Selection).

C-w (isearch-yank-word-or-char) appends the next
character or word at point to the search string. This is an easy way
to search for another occurrence of the text at point. (The decision
of whether to copy a character or a word is heuristic.)

Similarly, M-s C-e (isearch-yank-line) appends the rest
of the current line to the search string. If point is already at the
end of a line, it appends the next line. With a prefix argument
n, it appends the next n lines.

If the search is currently case-insensitive, both C-w and
M-s C-e convert the text they copy to lower case, so that the
search remains case-insensitive.

C-M-w (isearch-del-char) deletes the last character
from the search string, and C-M-y (isearch-yank-char)
appends the character after point to the search string. An
alternative method to add the character after point is to enter the
minibuffer with M-e (see Repeat Isearch) and type C-f
at the end of the search string in the minibuffer.